prometheus

Description

With prometheus you export metrics from CoreDNS and any plugin that has them.
The default location for the metrics is localhost:9153. The metrics path is fixed to /metrics.
The following metrics are exported:

Each counter has a label zone which is the zonename used for the request/response.

Extra labels used are:

server is identifying the server responsible for the request. This is a string formatted
as the server’s listening address: <scheme>://[<bind>]:<port>. I.e. for a “normal” DNS server
this is dns://:53. If you are using the bind plugin an IP address is included, e.g.: dns://127.0.0.53:53.

proto which holds the transport of the response (“udp” or “tcp”)

The address family (family) of the transport (1 = IP (IP version 4), 2 = IP6 (IP version 6)).

The response_rcode_count_total has an extra label rcode which holds the rcode of the response.

If monitoring is enabled, queries that do not enter the plugin chain are exported under the fake
name “dropped” (without a closing dot - this is never a valid domain name).

This plugin can only be used once per Server Block.

Syntax

prometheus [ADDRESS]

For each zone that you want to see metrics for.

It optionally takes an address to which the metrics are exported; the default
is localhost:9153. The metrics path is fixed to /metrics.

Examples

Use an alternative address:

. {
prometheus localhost:9253
}

Or via an environment variable (this is supported throughout the Corefile): export PORT=9253, and
then:

. {
prometheus localhost:{$PORT}
}

Bugs

When reloading, the Prometheus handler is stopped before the new server instance is started.
If that new server fails to start, then the initial server instance is still available and DNS queries still served,
but Prometheus handler stays down.
Prometheus will not reply HTTP request until a successful reload or a complete restart of CoreDNS.